A light emitting diode (which will be referred to herein as an “LED chip”) is a semiconductor device that can radiate an emission in a bright color with high efficiency even though its size is small. The emission of an LED chip has an excellent monochromatic peak. To produce white light from LED chips, a conventional LED lamp arranges red, green and blue LED chips close to each other and gets the light rays in those three different colors diffused and mixed together. An LED lamp of this type, however, easily produces color unevenness because the LED chip of each color has an excellent monochromatic peak. That is to say, unless the light rays emitted from the respective LED chips are mixed together uniformly, color unevenness will be produced inevitably in the resultant white light. Thus, to overcome such a color unevenness problem, an LED lamp for producing white light by combining a blue LED chip and a yellow phosphor was developed (see Patent Documents Nos. 1 and 2, for example).
According to the technique disclosed in Patent Document No. 1, white light is produced by combining together the emission of a blue LED chip and the yellow emission of a yellow phosphor, which is produced when excited by the emission of the blue LED chip. That is to say, the white light can be produced by using just one type of LED chips. That is why the color unevenness problem, which arises when white light is produced by arranging multiple types of LED chips close together, is avoidable.
The LED lamp with the bullet-shaped appearance as disclosed in Patent Document No. 2 has a configuration such as that illustrated in FIG. 1. As shown in FIG. 1, the bullet-shaped LED lamp 200 includes an LED chip 121, a bullet-shaped transparent enclosure 127 to enclose the LED chip 121, and leads 122a and 122b to supply current to the LED chip 121. A cup reflector 123 for reflecting the emission of the LED chip 121 in the direction pointed by the arrow D is provided for the mount portion of the lead 122b on which the LED chip 121 is mounted. The LED chip 121 is encapsulated with a first resin portion 124, in which a phosphor 126 is dispersed and which is further covered with a second resin portion 125. If the LED chip 121 emits a blue light ray, the phosphor 126 is excited by the blue light ray to produce a yellow light ray. As a result, the blue and yellow light rays are mixed together to produce white light.                Patent Document No. 1: Japanese Patent Application Laid-Open Publication No. 10-242513        Patent Document No. 2: Japanese Patent No. 2998696        